A student is attempting to dissolve a solid for a recrystallization. The student
ID: 878970 • Letter: A
Question
A student is attempting to dissolve a solid for a recrystallization. The student is told how much solid is present and how soluble the solid is in the solvent at the boiling point of the solvent. The student calculates how much solvent is required to just dissolve the entire sample, and measures out that exact amount of solvent. She then heats it to boiling, and slowly and carefully adds it to the solid, one drop at a time, keeping the mixture boiling the whole time. To her annoyance, when this is complete, not all of the solid has dissolved. What went wrong?
Explanation / Answer
Solution :-
When the student heated the solution to the boiling boilint and then started addind the solute then the amount of the solvent exactly needed to dissolve all the solid decreases in the due course of time while boiling the solvent becuase when the solvent is boiled then it get evaporated. Therefore the amount of the solvent present is decreased because of the boiling. Which causes decrease in the amount of the solvent and therefore at the end of the addition of the solvent to solid solute the amount of solvent needed to completely dissolve the solid is less which causes some of the solid remain undissolved.
Also the solid is soluble at the boiling point therefore after heating the solvent to boiling point student started addiding solvent slowly 1 drop at each time this will take some time which will cause decrease in the temperature of the solvent in the due course of time therefore the temperature of the solvent needed to dissolve the solid is no longer remain the same therefore it also causes the solid remain undissolved at the end of addition of the solvent.
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